Power modules integrate switching devices with further electrical circuit components in a single package for use in inverters, switching rectifiers or other power converters. High voltage power modules provide single package solutions for full or half-bridge circuits or multi-phase converters in a large form factor package used in high voltage power conversion applications. Many power modules are rated for operation at 1 kW or more, and heatsink components are often connected to the power module to dissipate thermal energy to maintain proper operating temperature of the integrated power switches. For high voltage systems, moreover, minimum spacing distances are required for physical separation of high-voltage components. Isolation specifications typically require electrically insulating encapsulation materials such as molded plastic to construct the integrated power module. However, the encapsulation material is typically a thermal insulator, and heat removal is accomplished by thermal conduction through an external heatsink bolted or otherwise mounted onto the integrated power module package to dissipate heat from one face of a switch component die through a substrate which is connected to the heatsink.
For low voltage power modules, molded resin plastic material encapsulates a power switch and other included circuit components to provide an unexposed structure having a relatively high thermal junction coefficient θjc. There are also low voltage power modules with exposed structures to increase heat dissipation using external heat sinks, for example, when heat sinking to a circuit board is not enough due to the power loss of the module. Some such packaging approaches include the use of an exposed ceramic substrate to reduce the thermal coefficient θjc. However, this approach increases module cost. FIG. 19 shows a high voltage power module 300 including a molded resin body 302 with a chip 304 including a semiconductor switching device (e.g., transistor) with connections to a lead frame 306 along with an integrated driver chip or IC 308 and a diode D. Wire bonding interconnections 320 connect the power switch chip 304 with the diode D and the driver chip 308, with the lead frame 306 providing external connections to other circuitry on a host circuit board (not shown). A substrate 310 is mounted to the lead frame 306 with an externally exposed substrate surface allowing interfacing with an external heatsink (not shown) to dissipate power from the power switch 304 and the diode D. As further shown in FIG. 20, direct bonded copper (DBC) approaches provide a conductive copper structure 312 mounted to the substrate 310 and exposed for connection to an external heatsink (not shown) to further reduce the thermal junction coefficient θjc. However, DBC techniques involve a further trade off with respect to higher module substrate cost and manufacturing complexity and a reduced supply chain of available vendors. Thus, lowering the thermal junction resistance θjc allows higher current carrying capacity for a given application but increases the component cost.
The individual components within power modules are interconnected using wire bonding techniques. For high current interconnections, the use of multiple low impedance gold wires is often cost-prohibitive, and lower cost heavy gauge aluminum wire or ribbon wiring interconnections are often used instead. These wire-based interconnections, however, result in parasitic impedances which can adversely impact performance of the converter system in which the power module is used.